Saint Paul remains topical today in a way that no one else in the Bible (with the admitted exception of God) can rival. Whenever tensions rise between the rival claims of Christian and secular morality, it is a fair bet that there will be a Pauline maxim lurking somewhere in the background.

Conservatives in the Church of England who fret about women bishops, and vicars who instruct their female parishioners to submit to their husbands, are consciously echoing Paul's first letter to Timothy: "I do not permit a woman to teach or to have authority over a man; she must be silent."

Meanwhile, when Catholics complain about their adoption agencies being obliged to consider gay couples as potential parents, it is the apostle's first letter to the Corinthians, in which he sternly condemns "arsenokoitai", or "men who double as women", that is surely uppermost in their minds. Paul, to those who reject the claims of organised religion, can often seem their worst nightmare: a choleric, ­finger-wagging bigot.

Yet such an image is a travesty. The supreme paradox about Paul is that the same apparently post-Christian values which have rendered him such a ­figure of suspicion to liberals are no less ­definitively informed by his ­teachings than are the harrumphings of anti-feminists and homophobes.

There is no moral presumption more fundamental to our society nowadays, perhaps, than that all humans should be treated and valued equally – and yet so utterly do we take this for granted that we can sometimes overlook just how culturally determined it is. When Paul declared to the Galatians that "there is neither Jew nor Greek, slave nor free, male nor female", he was proclaiming a message that was, in the context of the age, profoundly and disconcertingly novel.

The measure of Christ's love, so he declared, was that it had served to dissolve all differences of ethnicity, class and gender. This, to Paul, was "euangelion": "good news". To many people, however in a world that dismissed foreigners as barbarians, slaves as breathing machines, and women as biologically retarded versions of men, it was threatening in the extreme. Paul was preaching to the very opposite of the converted.

No wonder, then, in the opinion of most scholars, that it should have been his very own followers, a couple of ­generations on from his death, who actually wrote the letter to ­Timothy, in an attempt to moderate the radicalism of the apostle's teachings on the role of women.

Indeed, even Paul himself, it can often seem from reading through his letters, might sometimes all of a sudden find himself unsettled by the implications of the upheaval that he was preaching, and reach for the ­comfort blanket of his own inherited moral presumptions.

But if he frequently laid down laws, then so also, no less often, would he rip them up. Like anyone, he had his prejudices – and these, indisputably, have been part of the west's inheritance from him. But he was also a revolutionary – and it is the very measure of what he ultimately achieved that we should sometimes fail to recognise him as such.

Certainly, whenever we, in our own perplexity, debate how far we should push against the limits of our preconceptions in the name of equality and of love, we are doing as Paul himself, almost 2,000 years ago, so ­fatefully did.

The Bible: A History - St Paul, presented by Tom Holland, is on Channel 4 on Sunday 28 February at 7pm